cubicweb-vcsfile #3762947 debug reload in CW 3.19 breaks 'refresh repo' looping task [validation pending]

For some mind-boggling reason, CW 3.19 breaks the looping task after a reload (when in debug mode). Python's warn module - the one raising the exception at the heart of the bug - being partly written in C, it's quite difficult to precisely pinpoint the location of the bug.

The solution (and hopefully the correct one after 3 or 4 failed attempts) is to call import in the looping task's callback to make sure that we're always calling the latest _refresh_repo function from even after a reload.

done in1.15.0
load left0.000
closed by#9969eb748214 [hooks] Fix looping task on reload with CW 3.19 (closes #3762947)
patch[hooks] Fix looping task on reload with CW 3.19 (closes #3762947) [applied]